An X-ray analysis apparatus irradiates a sample mounted on a sample stage with primary X-rays, detects secondary X-rays such as fluorescent X-rays, scattering X-rays and the like generated at that time by means of an X-ray detector, processes properly the detected output, and thereby makes it possible to analyze constituent elements of the sample or its internal structure.
Recently a demand for analyzing in more detail a microscopic part of a sample, using the X-ray analysis apparatus as described above, has been increased. To perform this more detailed analysis, a microscopic part of the sample is irradiated with X-rays narrowed down by means of an X-ray guide member such as an X-ray guide tube and the like. In this case it is desirable to observe what position of the sample is irradiated with the narrow-diameter X-ray beam by means of an observing means such as a CCD camera and the like, and display the observed image on the display screen of a display device attached to an arithmetic and control device such as a personal computer and the like for controlling the whole apparatus.
Exemplary conventional X-ray analysis apparatus are described in Japanese Patent Laid-Open Publication No. Hei 4-175648 and Japanese Patent Laid-Open Publication No. Hei 6-288941. FIG. 6 shows schematically an X-ray analysis apparatus disclosed in Japanese Patent Laid-Open Publication No. Hei 4-175648, and in this X-ray analysis apparatus there are provided an X-ray tube 42 and an X-ray detector 43 so as to be opposite to each other obliquely above a sample 41, so that characteristic X-rays (fluorescent X-rays for example) 46 generated when the sample 41 is irradiated with X-rays (primary X-rays) 44 which have been emitted from the X-ray tube 42 and narrowed down by an X-ray guide member 45A are detected by means of the X-ray detector 43, and a CCD camera 47 as a sample observing means is provided directly above the sample 41 so as to observe an optical image (visible light image) of the sample 41 in a different direction (inclined direction) from the direction of irradiation of the X-rays 44 (the X-ray irradiation axis).
FIG. 7 shows schematically an X-ray analysis apparatus disclosed in Japanese Patent Laid-Open Publication No. Hei 6-288941 and this X-ray analysis apparatus provides an X-ray tube 42 and an X-ray guide member 45B, such as a collimator, directly above a sample 41, further provides a half mirror 48 made of beryllium leaf being low in X-ray absorptivity below the X-ray guide member 45B so that it makes an angle of 45° with the direction of X-ray irradiation, provides a CCD camera 47 at the reflecting surface side of it, and thereby makes it possible to observe an optical image (visible light image) of the sample 41 coaxially with the axis of X-ray irradiation. In FIGS. 6 and 7, number 49 refers to a tank containing a cooling medium for cooling the X-ray detector 43.
As shown in FIG. 6 described above, however, in an X-ray analysis apparatus made to observe an optical image at an angle with the direction of X-ray irradiation, when the height of a sample is changed, a difference (discrepancy) arises between the position of observing an optical image and the position of X-ray irradiation in the sample 41, and if the surface of the sample is uneven it is not possible to exactly determine the position of analysis. And even in case that the surface of a sample is not uneven, since the position of analysis is determined depending on the accuracy of determining the height of the sample 41, a mechanism for accurately setting the height is required, requiring thereby an apparatus that is complex in structure.
On the other hand, in the X-ray analysis apparatus shown in FIG. 7, since an optical image (visible light image) of a sample 41 is observed coaxially with the axis of X-ray irradiation, a disadvantage as described above in connection with the apparatus illustrated in FIG. 6 does not occur, but since the sample 41 is irradiated with X-rays 44 through the half mirror 48, even in case of using a material being low in X-ray absorptivity like beryllium leaf, at least some of the X-rays 44 are absorbed. Particularly, the lower the low-energy X-rays effective for exciting light elements are in energy, the more likely the X-rays are to be absorbed; it is not possible to avoid the lowering of analysis sensitivity in light element analysis. And it is unavoidable that the distance between the X-ray output end (the lower end 45b of the X-ray guide member 45B in this example) and the sample 41 is made larger by arranging the half mirror 48, and thereby the spatial resolution of the apparatus is lowered.
The present invention addresses the above-mentioned deficiencies, and an object of the invention is to provide an X-ray analysis apparatus and method being capable of simply and accurately determining the position of analysis in a sample from an optical image of it without lowering the sensitivity and the spatial resolution in light element analysis.